Ti-6Al-4V 합금의 양극산화와 석회화 순환 처리에 의한 표면 개질

Abstract

The purpose of this study was to investigate the bioactivity of Ti-6Al-4V alloy, which was modified by an anodic oxidation and an cyclic precalcification treatments. The electrolyte solution was prepared by mixing 79 wt% ethylene-glycol with 20 wt% distilled water and 1 wt% NH4F. The anodic oxidation process was conducted at a constant potential of 10, 15, 20, and 25 V for 1 h at room temperature. A cyclic precalcification treatment was done by soaking in 0.05 M NaH2PO4 solution at 80℃ and saturated Ca(OH)₂ solution at 90℃ in turns. All samples were heat-treated at 500℃ for 2 hours. Bioactivity was evaluated by apatite forming ability in a simulated body fluid (SBF). The average diameter of nanotubes increased with increasing the applied voltage. The growth of nanotubes has slowed after 10 minutes following the rapid growth in the initial stage. Nanotubes had self-aligned form with dense structure composed of small and large diameter, their diameter at the bottom was bigger than that at the top. Bioactivity was accelerated through the cyclic calcification treatment in 0.05M NaH₂PO₄ solution at 80℃ and saturated Ca(OH)₂ solution at 90℃. In conclusion, it is the effective surface treatment method of Ti-6Al-4V alloy for improvement of bioactivity that calcium phosphate is precipitated by cyclic calcification in 0.05M NaH₂PO₄ solution at 80℃ and saturated Ca(OH)2 solution at 90℃ after formation of TiO₂ nanotubes in ethylene-glycol solution at 25 V.